[PATCH v5 1/1] media: Documentation: Improve LINK_FREQ documentation

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Add a reference to the LINK_FREQ control and clarify the meaning of the
control as for C-PHY the matter is less obvious.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Mirela Rabulea <mirela.rabulea@nxp.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
I'm posting this separately from the metadata preparation series.

since v4 metadata preparation:

- Add the dependency to UI for CSI-2.

 Documentation/driver-api/media/tx-rx.rst                     | 3 ++-
 .../userspace-api/media/v4l/ext-ctrls-image-process.rst      | 5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/driver-api/media/tx-rx.rst b/Documentation/driver-api/media/tx-rx.rst
index 22e1b13ecde9..7df2407817b3 100644
--- a/Documentation/driver-api/media/tx-rx.rst
+++ b/Documentation/driver-api/media/tx-rx.rst
@@ -93,7 +93,8 @@ where
    * - variable or constant
      - description
    * - link_freq
-     - The value of the ``V4L2_CID_LINK_FREQ`` integer64 menu item.
+     - The value of the :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` integer64
+       menu item.
    * - nr_of_lanes
      - Number of data lanes used on the CSI-2 link.
    * - 2
diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
index 6d516f041ca2..57c2baf34acf 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
@@ -24,7 +24,10 @@ Image Process Control IDs
 .. _v4l2-cid-link-freq:
 
 ``V4L2_CID_LINK_FREQ (integer menu)``
-    The frequency of the data bus (e.g. parallel or CSI-2).
+    The fundamental frequency of the operating symbol rate (serial interfaces
+    such as CSI-2) or the sampling rate (parallel interfaces such as DVP or
+    Bt.565) of the data interface. For CSI-2, the frequency is equal to
+    _1 / (2 * UI)_.
 
 .. _v4l2-cid-pixel-rate:
 
-- 
2.47.3